Investigators in this section have begun to refine existing methodologies for the study of cortical functioning on the basis of positron emission tomography (PET) and electrical brain mapping procedures in humans. As wide variability has been noted in normals and patient groups in terms of PET determinations of cerebral glucography, additional effort has been forthcoming to control for behavioral variability and psychological task in these studies. This has included the use of somatosensory stimulus paradigms. Using some previously available PET methodologies and some new approaches, schizophrenic and affectively disordered patients appear to differ from normals. Psychiatric patients appear to have somewhat lower ratios of frontal to posterior cortical rates of glucose metabolism. However, the interpretation of these findings is obscure as these ratios do not represent an absolute lowering of glucose metabolic rates in the frontal cortex of psychiatric patients. Other preliminary findings suggest that schizophrenic patients appear to have lower glucose metabolism rates in the left central gray matter structures of the brain but elevated metabolism in both temporal lobes. By electrophysiology, a diminution of the N120 component of the somatosensory evoked potential has been observed in normals in response to a series of similar somatosensory stimuli. This habituation which is most prominent in somatosensory area II does not appear to occur in schizophrenic patients.